Various composites useful for altering magnetic fields have been disclosed in the art. Such composites are described in, for example, U.S. Pat. Nos. 5,827,445; 5,828,940 and 9,105,382 B2, and U.S. Pat. Publ. Nos. 2005/0012652 A1 and 2006/0099454 A1. Additionally, various methods for forming porous polymer materials have been disclosed in the art. Such composites are described in, for example, U.S. Pat. Nos. 5,196,262 and 6,524,742 B1.